Buttress attachment for circular stapling device

ABSTRACT

A circular stapling device includes a circular anvil assembly and a circular cartridge assembly. The anvil assembly includes a cap and head. The cap is movable relative to the head. The head supports a crush ring member that is movable into engagement with the cap to move the cap to an unapproximated position relative to the head to release a portion of an anvil buttress member supported between the anvil cap and the anvil head. The cartridge assembly includes a housing, a pusher member, a retaining ring member, and a fastener cartridge. The retaining ring member releasably secures a portion of a cartridge buttress member to one or both of the housing and the fastener cartridge. The retaining ring member releases the cartridge buttress member when the retaining ring member moves from a radially constricted condition to a radially expanded condition in response to a movement of the pusher member.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.13/758,120, filed Feb. 4, 2013, now U.S. Pat. No. 9,414,839, the entirecontent of which is incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to surgical stapling devices and, moreparticularly, to structures and methods for removably attaching buttressmaterial to circular surgical stapling devices for use in anastomosisprocedures.

BACKGROUND

Fasteners have traditionally been used to replace suturing when joiningvarious body structures such as, for example, the bowel or bronchus.Surgical stapling devices employed to apply these fasteners aregenerally designed to simultaneously cut and seal tissue to reduce thetime and risks involved with anastomosis procedures.

Circular surgical stapling devices are employed by surgeons tosequentially or simultaneously apply one or more surgical fasteners,e.g., staples or two-part fasteners, to body tissue for the purpose ofjoining segments of body tissue together and/or for the creation ofanastomoses. Circular surgical stapling devices generally include anannular fastener cartridge assembly that supports a plurality of annularrows of fasteners, an annular anvil assembly operatively associated withthe fastener cartridge assembly which provides a surface against whichthe fasteners are formed upon a firing of the circular stapling device,and an annular blade for cutting tissue.

For most procedures, the use of bare fasteners, with the fasteners indirect contact with the patient's tissue, is generally acceptable. Theintegrity of the tissue will normally serve to prevent the fastenersfrom tearing out of the tissue and compromising the sealing beforehealing has occurred. However, in some surgical operations buttressmaterials are employed by surgeons in combination with circular staplingdevices to bridge, repair and/or reinforce tissue defects within apatient. In particular, buttress materials reduce the trauma suffered bythe patient, reduce the instances of leakage, reduce the instances ofbleeding, and create a relatively strong bond between adjacent bodytissues.

Accordingly, there is a need for reliably and removably attachingbuttress material onto a circular stapling device so that the buttressmaterial does not interfere with the operation of the device, remains onthe device until after the fasteners are fired, and is convenient andeasy to install and use.

SUMMARY

According to one aspect, a circular stapling device includes a handleassembly, an elongate body that extends from the handle assembly, acartridge assembly mounted on a distal end portion of the elongate body,and a circular cartridge buttress member.

The cartridge assembly includes a housing, a pusher member supportedwithin the housing, a retaining ring member and a fastener cartridgebody supported on the housing, and a circular cartridge buttress member.The fastener cartridge body has a tissue engaging surface that extendsto an annular edge.

The pusher member is movable between a first position and a secondposition. The pusher member includes one or more ramp features extendingradially outward from an outer surface of the pusher member. The one ormore ramp features move the retaining ring member toward the radiallyexpanded condition when the one or more ramp features engage an innersurface of the retaining ring member. The housing defines one or morechannels that receive the one or more ramps. The one or more ramps aremovable in the one or more channels.

The retaining ring member is configured and arranged to move between aradially constricted condition and a radially expanded condition inresponse to movement of the pusher member. The housing defines a cutoutin an outer surface thereof within which the retaining ring member isseated when the retaining ring member is disposed in the radiallyconstricted condition.

The circular cartridge buttress member has a body portion and anextension portion. The body portion is supported on the tissue engagingsurface of the fastener cartridge. The extension portion extends fromthe body portion and over the annular edge of the tissue engagingsurface. The retaining ring member secures the extension portion againstone or both of the fastener cartridge body and the housing when in theradially constricted condition. The retaining ring member releases theextension portion when the retaining ring member moves to the radiallyexpanded condition in response to a movement of the pusher member fromthe first position to the second position so that the body portion ofthe cartridge buttress separates from the tissue engaging surface of thefastener cartridge body.

In embodiments, the retaining ring member is a split ring. The splitring includes a pair of ends, each end being disposed in at leastrelatively close approximation with one another when the split ring isdisposed in the radially constricted condition. The ends separate fromone another when the split ring is disposed in the radially expandedcondition.

The split ring includes a plurality of spaced apart tabs extending froma top edge of a body of the split ring. The plurality of spaced aparttabs engages a bottom surface of the fastener cartridge body. Aclearance is defined between adjacent tabs of the plurality of spacedapart tabs, the bottom surface of the fastener cartridge body, and thetop edge of the body of the split ring. The extension portion of thecartridge buttress member includes a plurality of sections. Theclearance is adapted to receive one or more sections of the extensionportion to secure the one or more sections of the extension portionbetween the fastener cartridge body and the split ring. Movement of thepusher member into engagement with the split ring expands the split ringradially outwardly and creates a radial clearance sufficient to releasethe one or more sections of the extension portion from between thefastener cartridge body and the split ring so that the cartridgebuttress member separates from the fastener cartridge body upon thefiring of fasteners from the fastener retaining slots defined within thefastener cartridge body.

In accordance with another aspect, an anvil assembly includes a circularanvil head, an anvil cap, and a circular anvil buttress member. Thecircular anvil head has a first engaging feature and supports a crushring member.

The anvil cap has a second engaging feature that connects with the firstengaging feature of the anvil head to secure the anvil cap to the anvilhead. The anvil cap is movable relative to the anvil head between anapproximated position and an unapproximated position. The crush ringmember is spaced from the second engaging feature when the anvil cap isdisposed in the approximated position and movable into engagement withthe second engaging feature to move the anvil cap to the unapproximatedposition.

The circular anvil buttress member includes a body portion and anextension portion that extends from the body portion. The body portionis supported on a tissue engaging surface of the anvil head. Theextension portion is secureable between the anvil cap and the anvil headwhen the anvil cap is disposed in the approximated position. Theextension portion is releasable from between the anvil cap and the anvilhead when the anvil cap is disposed in the unapproximated position sothat the body portion separates from the tissue engaging surface of theanvil head. In the unapproximated position, the anvil cap and the anvilhead define a gap therebetween dimensioned to permit the extensionportion to release from between the anvil cap and the anvil head. In theapproximated position, the gap is dimensioned to enable the anvil capand the anvil head to trap the extension portion therebetween.

The anvil cap includes a snap feature and the anvil head defines a firstrecess and a second recess. The snap feature is selectively positionablewithin one of the first recess and the second recess. The snap featureis positionable within the first recess when the anvil cap is disposedin the approximated position and is positionable within the secondrecess when the anvil cap is disposed in the unapproximated position.The first recess and the second recess are separated by a rampedpartition. The snap feature cams over the ramped feature as the anvilcap moves from the approximated position to the unapproximated position.The snap feature flexes outwardly from the first recess as the snapfeature cams over the ramped partition and flexes inwardly into thesecond recess after camming over the ramped partition. The snap featuremaintains the anvil cap secured to the anvil head when the snap featureis disposed in the second recess. The snap feature defines an openingdisposed radially outwardly of the snap feature that permits the snapfeature to flex outwardly relative to a body of the anvil cap. Inembodiments, the anvil cap includes a plurality of spaced apart snapfeatures.

According to another aspect, a method for releasing an anvil buttressmember from an anvil assembly of a circular stapling device includes thestep of providing a circular stapling device including an elongatemember having an end effector mounted on a distal end portion of theelongate body. The end effector includes an anvil assembly that includesan anvil head and an anvil cap that support an extension portion of ananvil buttress member therebetween so that a body portion of the anvilbuttress member is supported on a tissue engaging surface of the anvilhead. The method involves moving the anvil cap relative to anvil head torelease the anvil buttress member from the anvil assembly.

The method includes releasing the extension portion of the anvilbuttress member from being trapped between the anvil cap and the anvilhead. One step involves moving a crush ring member supported on theanvil head into engagement with the anvil cap to move the anvil caprelative to the anvil head. Another step includes spacing the anvil capand the anvil head relative to one another in response to engagement ofthe crush ring member with the anvil head to provide a gap between theanvil cap and the anvil head sufficient to enable the extension portionof the anvil buttress member to be released from between the anvil capand the anvil head.

Other aspects, features, and advantages will be apparent from thedescription, drawings, and claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosureand, together with a general description of the disclosure given aboveand the detailed description given below, serve to explain theprinciples of the disclosure, wherein:

FIG. 1 is a perspective view of a circular surgical stapling deviceaccording to the present disclosure;

FIG. 2 is an enlarged perspective view illustrating the indicated areaof detail shown in FIG. 1;

FIG. 3 is an enlarged perspective view, with parts separated, of acartridge assembly of the presently disclosed circular surgical staplingdevice;

FIG. 4 is a partial side cross-sectional view of the cartridge assembly,the cartridge assembly being shown in a first configuration;

FIG. 5 is an enlarged cross-sectional view illustrating the indicatedarea of detail shown in FIG. 4;

FIG. 6 is a top cross-sectional view of the cartridge assembly takenalong line 6-6 of FIG. 5;

FIG. 7 is a partial side cross-sectional view of the cartridge assembly,the cartridge assembly being shown in a second configuration;

FIG. 8 is an enlarged cross-sectional view illustrating the indicatedarea of detail shown in FIG. 7;

FIG. 9 is a top cross-sectional view of the cartridge assembly takenalong line 9-9 of FIG. 8;

FIG. 10 is a top perspective view of an anvil assembly and a shaftmember of the presently disclosed circular surgical stapling device;

FIG. 11 is a bottom perspective view of the anvil assembly and a portionof the shaft member;

FIG. 12 is a perspective view, with parts separated, of the anvilassembly and the shaft member;

FIG. 13 is a cross-sectional view of the anvil assembly and a distalportion of the shaft member, the anvil assembly being shown in a firstconfiguration;

FIG. 14 is a cross-sectional view of the anvil assembly and a distalportion of the shaft member, the anvil assembly being shown in a secondconfiguration; and

FIG. 15 is a cross-sectional perspective view of an anastomotic tissuesite, the anastomotic tissue site being shown with buttress material ofthe presently disclosed circular stapling device secured thereto duringa surgical procedure effectuated with the presently disclosed circularstapling device.

DETAILED DESCRIPTION

As used herein, the term “clinician” refers to a doctor, a nurse, or anyother care provider and may include support personnel. Particularembodiments of the present disclosure will be described herein withreference to the accompanying drawings. As shown in the drawings and asdescribed throughout the following description, and as is traditionalwhen referring to relative positioning on an object, the term “proximal”refers to the end of the device that is closer to the clinician and theterm “distal” refers to the end of the device that is farther from theclinician. In the following description, well-known functions orconstructions are not described in detail to avoid obscuring the presentdisclosure in unnecessary detail.

Referring initially to FIG. 1, a circular surgical stapling device foruse with a buttress material is disclosed herein and is generallydesignated as 10. In embodiments, the surgical stapling device 10 isadapted for reuse and in certain embodiments; the surgical staplingdevice 10 is adapted for a single use and can be disposable.

The circular stapling device 10 includes a handle assembly 20, a tubularelongate body 30, and an end effector 40. The handle assembly 20includes a rotatable advancing member 22 and a pivotable trigger member24 that are operatively coupled to any number of drivers supported bythe surgical stapling device 10 to effectuate a firing of the surgicalstapling device 10.

In any of the embodiments disclosed herein, the handle assembly mayinclude a source of power, such as a motor and battery, may beconnectable to an external power source, or a remote control unit.

The elongate body 30 extends distally from a distal end portion of thehandle assembly 20 to a proximal end portion of the end effector 40 sothat the elongate body 30 is disposed between the handle assembly 20 andthe end effector 40. In some embodiments, the elongate body 30 has alinear shape along the length of the elongate body 30, and in certainembodiments, the elongate body 30 has a curved shape along the length ofthe elongate body 30.

The end effector 40 includes a fastener cartridge assembly 100, an anvilassembly 200, and a shaft 300. The shaft 300 includes a proximal endportion that is secured to the fastener cartridge assembly 100 and adistal end portion that is secured to the anvil assembly 200. In certainembodiments, the fastener cartridge assembly 100 and/or the anvilassembly 200 may be replaced and the circular stapling device 10 may bereused. The end effector 40 supports a knife assembly with asubstantially cylindrical knife 400 (FIG. 14) adapted to cut tissue.

Reference may be made to U.S. Pat. No. 5,915,616 to Viola et al. andcommonly owned U.S. Patent Application Publication No. 2011/0174099, theentire contents of which are incorporated herein by reference, for adetailed discussion of the construction and operation of exemplarycircular stapling devices.

Turning now to FIGS. 2-3, the cartridge assembly 100 includes a housing110, a retaining ring member 120, a fastener cartridge body 130, acircular cartridge buttress 140, and a pusher member 150.

The housing 110 has a generally tubular shell body 112 with an outersurface 112 a and an inner surface 112 b. The shell body 112 extendsdistally to a plurality of arms 114 that extend radially about thecircumference of the distal end portion of the shell body 112. Each arm114 includes a first shoulder 114 a and a second shoulder 114 b that arerecessed from the outer surface of the housing 110. Each shoulder may berecessed to any suitable depth. For example, the first shoulders 114 aand the second shoulders 114 b may be recessed at different depths fromthe outer surface of the housing 110. In particular, the first shoulders114 a may be recessed at a first depth to define a first annular cutout,channel, or race and the second shoulders 114 b may be recessed at asecond depth to define a second annular cutout, channel, or racedifferent from the first annular cutout. The first annular cutout isdimensioned to receive the retaining ring member 120 and the secondannular cutout is dimensioned to receive at least part of an extensionportion 144 of the cartridge buttress member 140 as described in greaterdetail below. Each arm 114 is disposed in spaced-apart relationship withadjacent arms 114. Adjacent arms 114 define a channel 116 therebetween.At least some of the arms 114 define an opening 114 c that extendsthrough the respective arm 114.

The retaining ring member 120 is supported on the outer surface 112 a ofthe housing 110 and is dimensioned to move relative to the tubular shellbody 112 of the housing 110 between a radially constricted condition anda radially expanded condition in response to movement of the pushermember 150 to selectively retain or release the circular cartridgebuttress 140 on or from the fastener cartridge body 130 as described ingreater detail below. The retaining ring member 120 (e.g., a split ring)has an annular body 122 that extends radially between a pair of endportions 124 including a first end portion 124 a and a second endportion 124 b. In the radially constricted condition, the end portions124 are in contact or are disposed in relatively close approximationwith one another. As the retaining ring member 120 moves from theradially constricted condition to the radially expanded condition, theend portions 124 separate from one another such that the end portions124 are spaced from one another in the radially expanded condition.Notably, any space between the end portions 124 that may be providedwhen the retaining ring member 120 is in the radially constrictedcondition is increased as the end portions 124 move toward the radiallyexpanded condition.

As seen in FIG. 3, the retaining ring member 120 includes a plurality ofspaced apart tabs 126 that extend from a top edge 122 a of the body 122.The plurality of spaced apart tabs 126 are dimensioned to engage abottom surface of the fastener cartridge body 130 such that a clearanceis defined between adjacent tabs of the plurality of spaced apart tabs126, the bottom surface of the fastener cartridge body 130, and the topedge 122 a of the body 122 of the retaining ring member 120 when theplurality of spaced apart tabs 126 are engaged with the bottom surfaceof the fastener cartridge body 130. The clearance is dimensioned toreceive a part or parts of an extension portion 144 of the circularcartridge buttress member 140 to secure the extension portion 144between the fastener cartridge body 130 and the ring retaining member120.

The fastener cartridge body 130 is supported on the housing 110 andincludes an annular body 132. The annular body 132 is received in adistal end portion of the housing 110. Fastener cartridge body 130includes a tissue engaging surface 134 that extends to an annular edge134 a. A plurality of fastener retaining slots 136 are defined withinthe tissue engaging surface 134 and arranged in one or more concentricand/or annular arrays. Each fastener retaining slot 136 is dimensionedto receive a fastener 50 (FIG. 4). The annular body 132 includes one ormore detents 138 a that extends from a sidewall 138 thereof. Each detent138 a is dimensioned to engage an opening 114 c of the arms 114 of thehousing 110 to secure the fastener cartridge body 130 to the distal endportion of the housing 110.

As seen in FIGS. 4 and 5, the circular cartridge buttress 140 isselectively supported on the fastener cartridge body 130 and includes abody portion 142 and an extension portion 144 that extends radiallyoutwardly from the body portion 144. The extension portion 144 mayinclude any number of sections. The body portion 142 is dimensioned tooverlie the tissue engaging surface 134 of the fastener cartridge body130. The extension portion 144 includes a plurality of spaced apartfingers 146 arranged annularly about the body portion 144. The extensionportion 144 is dimensioned to extend over the annular edge 134 a of thetissue engaging surface 134 of the fastener cartridge body 130 and ispositionable adjacent to the shoulder 114 b of the housing 110 betweenthe outer surface of one or more of the arms 114 of the housing 110 andthe inner surface of the retaining ring member 120 for securementbetween the retaining ring member 120 and the housing 110. The extensionportion 144 may be dimensioned to contact the shoulder 114 b. Asappreciated, the retaining ring member 120 secures the extension portion144 against one or both of the fastener cartridge body 130 and thehousing 110 when the retaining ring member 120 is in the constrictedcondition and releases the extension portion 144 when the retaining ringmember 120 moves to the expanded condition. For example, the retainingring member and pusher member can be arranged so that the retaining ringmember moves to the expanded condition in response to a movement of thepusher member 150 from a proximal position to a distal position asdescribed in greater detail below.

The pusher member 150 is movably mounted within housing 110 betweenproximal and distal positions. The pusher member 150 includes an annularpusher body 152 that has a plurality of pushers 154 disposed in aconcentric and/or annular array about the pusher body 152. One or moreramps 156 extend radially outwardly from an outer surface of at leastsome of the pushers 154.

Turning now to FIGS. 10-14, the anvil assembly 200 includes a circularanvil head 210, an anvil cap 220, a circular anvil buttress member 230,a crush ring member 240, and an anvil plate 250.

The circular anvil head 210 includes a head body 212 that supports thecrush ring member 240 and the anvil plate 250 on a proximal surface ofthe head body 212. The head body 212 has a connector 214 extendingproximally from the head body 212. The connector 214 is dimensioned tooperatively couple to a distal end portion 302 of the shaft member 300.One or more engaging passages 216 are defined by the head body 212 andextend through the head body 212. A distal surface of the head body 212includes one or more ramped partitions 218 that separate a first recess218 a and a second recess 218 b defined on opposite sides of rampedpartition 218.

The anvil cap 220 includes a cap body 222 that is supported on thedistal surface of the anvil head 210. The cap body 222 includes one ormore engaging features 224 and one or more snap features 226 that extendproximally from the cap body 222. The snap feature 226 includes a tooth226 a that extends inwardly. The first and second recesses 218 a, 218 bof the anvil head 210 are each dimensioned to receive the tooth 226 a tofacilitate securement of the anvil cap 220 to the anvil head 210. Thecap body 222 defines an opening 228 dimensioned to enable the snapfeature 226 to flex radially outwardly to permit the anvil cap 220 tomove relative to the anvil head 210 between approximated andunapproximated positions. (See FIG. 14, for example).

The anvil plate 250 secures to the proximal surface of the anvil head210 and has an annular body 252 that defines an opening 254therethrough. The annular body 252 has a tissue engaging surface 256that defines a plurality of fastener forming pockets 256 a. Theplurality of fastener forming pockets 256 a is arranged in an annulararray about the tissue engaging surface 256 of the annular body 252.

The circular anvil buttress member 230 is selectively supported on theanvil plate 250 and has an annular body portion 232 and an extensionportion 234 that extends radially from the body portion 232. The bodyportion 232 is dimensioned to overlie the tissue engaging surface 256 ofthe anvil plate 250 and defines a central opening 236 therethrough. Theextension portion 234 includes a plurality of spaced apart tabs 234 athat extend radially outwardly about the body portion 232. The pluralityof spaced apart tabs 234 a are selectively positionable between theproximal surface of the anvil cap 220 and the distal surface of theanvil head 210 to selectively secure the annular body portion 232against the tissue engaging surface 256 of the anvil plate 250 when theanvil cap 220 is disposed in the approximated position. As described ingreater detail below, the extension portion 234 is releasable from thebetween the anvil cap 220 and the anvil head 210 when the anvil cap 220is moved to the unapproximated position so that the body portion 232separates from the tissue engaging surface 256 of the anvil plate 250.

The crush ring member 240 is supported on the anvil head 210 andincludes a generally annular body 242 having a plurality of tab members244 that secure to a proximal surface of the anvil head 210 and extendfrom the body 242 at radially spaced locations along an outer surface ofthe body 242. The crush ring member 240 is dimensioned to be spaced fromthe one or more engaging features 224 of the cap body 222 when the anvilcap 220 is disposed in the approximated position and movable intoengagement with the one or more engaging features 224 when the anvil cap220 is moved to the unapproximated position. The annular body 242defines an aperture 246 therethrough that is dimensioned to receive theconnector 214 of the head body 212 when the crush ring member 240 issecured to the anvil head 210.

During operation of the surgical stapling device 10, the anvil assembly200 and the cartridge assembly 100 are approximated by the actuation ofadvancing member 22 until the anvil assembly 200 and the cartridgeassembly 100 are suitably clamped against tissue of a patient. Thetrigger member 24 is then actuated to fire the surgical stapling device10.

With reference to FIGS. 4-9, the pusher member 150, upon a firing of thesurgical stapling device 10, is distally advanced from a proximalposition by a drive assembly (not shown). As the pusher member 150distally advances, the plurality of pushers 150 advance through thefastener retaining slots 136 to engage and dispense the fasteners 50supported within the fastener retaining slots 136.

Additionally, as the pusher member 150 distally advances, the ramps 156thereof slide through the channels 116 of the housing 110 and intoengagement with the inner surface of the retaining ring member 120. Theramps 156 push the retaining ring member 120 radially outwardly from theradially constricted condition to the radially expanded condition of theretaining ring member 120. As the retaining ring member 120 moves to theradially expanded condition, a radial clearance or gap “G1” is createdbetween the retaining ring member 120 and the outer surface of thehousing 110 which frees the extension portion 144 of the cartridgebuttress 140. The distal driving force provided to the fasteners 50 fromthe pusher member 150 is imparted to the body portion 142 of thecircular cartridge buttress 140 which releases the circular cartridgebuttress 140 by drawing the extension portion 144 of the circularcartridge buttress 140 distally through the created space or gap “G1.”Upon release of the extension portion 144 of the cartridge buttress 140,the body portion 142 is separable from the tissue engaging surface 134of the fastener cartridge body 130.

Referring also to FIGS. 13-15, the driving force imparted on thefasteners 50 drives the legs of the fasteners 50 through cartridgebuttress member 140, the clamped tissue “T”, and anvil buttress member230 until the legs of the fasteners 50 are formed within the fastenerforming pockets 256 a of the anvil plate 250 to secure the cartridgebuttress 140 and the anvil buttress member 230 to the tissue “T” withthe fasteners 50. The knife 400 is simultaneously thereafter advancedinto the anvil assembly 200 to sever the tissue “T” and to distallyadvance the crush ring member 240. The distal movement of the crush ringmember 240 drives the crush ring member 240 into engagement with the oneor more engaging features 224 of the anvil cap 220 and separates theproximal surface of the cap body 222 of the anvil cap 220 from thedistal surface of the head body 212 of the anvil head 210. Inparticular, the teeth 226 a of the snap features 226 cam against theramped partitions 218 so that each snap feature 226 flexes radiallyoutwardly into the opening 228 of the cap body 222 from the first recess218 a of the head body 212 to enable the anvil cap 220 to separate fromthe anvil head 210 as the anvil cap 220 moves from the approximatedposition to the unapproximated position. After camming over the rampedpartitions 218, the teeth 226 a of the snap features 226 snap or flexesradially inwardly into the second recess 218 b of the head body 212 tomaintain the anvil cap 220 secured to the anvil head 210. The separationof the cap body 222 and the head body 212 creates a space or gap “G2”between the proximal surface of the cap body 222 and a distal surface ofthe head body 212 to free the extension portion 234 of the anvilbuttress member 230 from between the anvil head 210 and the anvil cap220 so that both of the anvil buttress member 230 and the cartridgebuttress member 140 are secured to the tissue “T” independent of thesurgical stapling device 10.

Persons skilled in the art will understand that the structures andmethods specifically described herein and illustrated in theaccompanying figures are non-limiting exemplary embodiments, and thatthe description, disclosure, and figures should be construed merely asexemplary of particular embodiments. It is to be understood, therefore,that the present disclosure is not limited to the precise embodimentsdescribed, and that various other changes and modifications may beeffected by one skilled in the art without departing from the scope orspirit of the disclosure. For example, in any of the embodimentsdisclosed herein, one or more curved arrays of staples can be providedin the fastener cartridge. Circular fastener cartridges, and curvedfastener cartridges are contemplated as are two or three rows ofstaples. Additionally, it is envisioned that the elements and featuresillustrated or described in connection with one exemplary embodiment maybe combined with the elements and features of another without departingfrom the scope of the present disclosure, and that such modificationsand variations are also intended to be included within the scope of thepresent disclosure. Indeed, any combination of any of the presentlydisclosed elements and features is within the scope of the presentdisclosure. Accordingly, the subject matter of the present disclosure isnot to be limited by what has been particularly shown and described.

The invention claimed is:
 1. An anvil assembly, comprising: a circularanvil head having a first engaging feature and supporting a crush ringmember; an anvil cap having a second engaging feature that connects withthe first engaging feature of the anvil head to secure the anvil cap tothe anvil head, the anvil cap being movable relative to the anvil headbetween an approximated position and an unapproximated position, thecrush ring member being spaced from the second engaging feature when theanvil cap is disposed in the approximated position and movable intoengagement with the second engaging feature to move the anvil cap to theunapproximated position; and a circular anvil buttress member includinga body portion and an extension portion that extends from the bodyportion, the body portion supported on a tissue engaging surface of theanvil head, the extension portion being secureable between the anvil capand the anvil head when the anvil cap is disposed in the approximatedposition, the extension portion being releasable from between the anvilcap and the anvil head when the anvil cap is disposed in theunapproximated position so that the body portion separates from thetissue engaging surface of the anvil head.
 2. The anvil assembly ofclaim 1, wherein the anvil cap includes a snap feature and the anvilhead defines a first recess and a second recess, the snap feature beingselectively positionable within one of the first recess and the secondrecess, the snap feature being positionable within the first recess whenthe anvil cap is disposed in the approximated position and beingpositionable within the second recess when the anvil cap is disposed inthe unapproximated position.
 3. The anvil assembly of claim 2, whereinthe first recess and the second recess are separated by a rampedpartition, the snap feature camming over the ramped partition as theanvil cap moves from the approximated position to the unapproximatedposition.
 4. The anvil assembly of claim 3, wherein the snap featureflexes outwardly from the first recess as the snap feature cams over theramped partition and flexes inwardly into the second recess aftercamming over the ramped partition, the snap feature maintaining theanvil cap secured to the anvil head when the snap feature is disposed inthe second recess.
 5. The anvil assembly of claim 1, wherein the anvilcap includes a plurality of spaced apart snap features.
 6. The anvilassembly of claim 1, wherein the anvil cap includes a snap feature, theanvil cap including a cap body that defines an opening disposed radiallyoutwardly of the snap feature, the opening configured to enable the snapfeature to flex outwardly relative to the cap body of the anvil cap. 7.The anvil assembly of claim 1, wherein in the unapproximated position,the anvil cap and the anvil head define a gap therebetween dimensionedto permit the extension portion to release from between the anvil capand the anvil head.
 8. The anvil assembly of claim 7, wherein in theapproximated position, the gap is dimensioned to enable the anvil capand the anvil head to trap the extension portion therebetween.